Operational Use of Prescribed Fire in
Southern California Chaparral1
Ron Dougherty and Philip J. Riggan2
Fire is a dominant natural feature in Mediterranean-type ecosystems throughout the world. With
their characteristic summer droughts and highly
flammable vegetation, these ecosystems are frequently coursed by catastrophic wildfires.
Nowhere is the threat to human life and property more acute than in the complex association of
wildland chaparral and developed urban areas in
southern California. Here, in November 1980, over
320 homes were destroyed and 36,000 ha of chaparral watershed were burned by major wildfires
raging under the influence of foehn-type Santa Ana
winds. These were not uncommon events; in modern
times, homes are destroyed and thousands of hectares are burned every year by wildfire. Loss of
life and property can be even greater in the
flooding and debris production that often follows
major chaparral fires.
Fire suppression and prevention programs have
reduced the frequency and size of wildfires, but
this approach alone has not prevented catastrophic
wildfires, and natural fire regimes may have been
altered, with profound effects upon this fireadapted ecosystem. In response to these problems,
efforts are being made to use fire under prescribed conditions to manage chaparral fuels and
provide positive resource benefits.
A program designed to develop and demonstrate
the use of prescribed fire and other management
techniques in the chaparral has been underway
since 1977 on the Laguna-Morena Demonstration Area
in San Diego County. This paper discusses the
rationale for prescribed burning in the chaparral
and associated ecosystems, presents an overview of
the operational planning needed for a successful
prescribed fire, and discusses our recent experience with this technique.
1
Presented at the Symposium on Dynamics and
Management of Mediterranean-type Ecosystems, June
22-26, 1981, San Diego, California.
Abstract: The use of prescribed fire in the
chaparral could reduce the incidence and impacts
of severe wildfires and enhance watershed resources. This paper describes the operational
planning needed for a successful prescribed fire
and discusses the recent experience with this
technique on the Cleveland National Forest.
PRESCRIBED FIRE OBJECTIVES
Fire Hazard Reduction
The use of prescribed fire in chaparral has
potential for reducing the occurrence, size, and
impact of large wildfires. Mosaics of differentaged chaparral stands can be produced and maintained by periodic burning under low to moderate
fire intensity conditions. These mosaics break up
large areas of heavy fuel accumulation and maintain a substantial area of chaparral in a young,
productive state. The occurrence and adverse
effects of large wildfires should be reduced since
fire propagation and resistance to control are
considerably less in well-stocked young stands
with their low dead fuel volumes (Rothermel and
Philpot 1973, Philpot 1974).
Areas of young chaparral have been useful in
the suppression of large wildfires burning under
extreme conditions. In 1979, the 1900-ha Monte
Fire in the Angeles National Forest was contained
on the south and west when driven by moderate
Santa Ana winds into areas burned 4 years previously by the Mill and Pacoima Fires. Fire
activity in the young age classes was greatly
reduced, with only uneven fire spread through
3
grass and light fuels on the north-facing slopes.
The southward advance of the 1980 Turner Fire in
and adjacent to the Trabuco District, Cleveland
National Forest, was halted under 30 to 50 km/h
winds when it reached an age-class boundary of the
4
1975 Tenaja Fire. The 1980 Thunder Fire in the
Mt. Baldy District, Angeles National Forest,
burned southward along San Antonio Canyon under
the influence of strong Santa Ana winds. Long
distance spotting into 27-year-old chaparral on
the east side of the canyon propagated the fire
and required sustained fire suppression action.
Spotting into chaparral burned during the 1975
Village Fire on the west side of the canyon produced only poorly propagating fires that presented
5
little resistance to control. While even young
stands of chaparral may propagate fire under the
most extreme conditions, both the resistance to
3
2
Assistant Fire Management Officer, Eldorado
National Forest, Placerville, Calif.; Soil Scientist, Pacific Southwest Forest and Range Experiment Station, Forest Service, U.S. Department of
Agriculture, Glendora, Calif.
Personal communication from C. Gripp, Angeles
National Forest, Flintridge, Calif.
4
Personal communication from M. Stout,
Cleveland National Forest, Santa Ana, Calif.
5
Personal communication from W. Hite, Angeles
National Forest, Glendora, Calif.
502
Gen. Tech. Rep. PSW-58. Berkeley, CA: Pacific Southwest Forest and Range
Experiment Station, Forest Service, U.S. Department of Agriculture; 1982.
control and potential for mid- and long-range
spotting are greatly reduced.
increased in some areas of coastal sage at the
urban interface.
These benefits are particularly valuable at the
wildland-urban interface where a mosaic of natural
and planted vegetation often presents extreme fire
hazards. Embers from large chaparral wildfires,
such as the highly destructive Stable and Panorama
Fires of 1980, can be carried a considerable
distance into the developed community by longrange spotting. Carefully applied prescribed
burning and age-class management in heavy chaparral adjacent to the interface could substantially
reduce this problem. Less is known about the
value of prescribed burning where the fuels are
coastal sage scrub.
A large-scale age-class management program
could be designed to substantially reduce the
adverse impacts of high intensity wildfire.
Prescribed fires can be conducted under weather
and fuel conditions chosen to minimize fire intensity and planned to encompass specific terrain of
limited area. Cooler fire temperatures reduce
nutrient loss (Dunn and DeBano 1977), soil water
repellency (DeBano 1981) and erosion (Wells, in
press), and seed destruction. Prescribed fires
frequently burn only 40 to 70 percent of the
vegetation within the fire perimeter, thus creating both a diversity of habitat and more nutrientrich browse that are favorable for wildlife
(Lillywhite 1977, Bissel and others 1955). The
area burned within major watersheds can also be
controlled, and this helps to reduce downstream
flooding potential. A planned sediment management
program using prescribed fire on important watersheds could be designed to minimize and regulate
debris production.
Prescribed fire can also be applied for the
protection of high-value riparian and woodland
resources. In stands of California live oak
(Quercus agrifolia Nee), substantial mortality in
younger age classes can occur during severe wildfires, and larger trees can suffer damage to the
cambium and lower stem that makes them more susceptible to disease and insects (Plumb 1980).
California black oak (Quercus kelloggii Newb.) is
more susceptible and can be largely topkilled
during wildfire. Understory prescribed burning
can be successfully applied in stands of these
species to reduce fuel accumulations (Green 1980)
and provide protection against severe wildfires.
Understory burning may also encourage seedling
regeneration in areas of heavy litter accumulation, aid in the control of forest pathogens
(Parmeter 1977), and mineralize nutrients in the
forest floor litter.
Serious fire hazard problems also exist in many
of the coniferous forest areas of southern California. Before 1905, ponderosa (Pinus ponderosa
Laws.) and Jeffrey (Pinus jeffreyi Grev. and
Balf.) pine stands in the San Bernardino Mountains
were coursed by low intensity fires at a frequency
averaging 10 to 12 years (McBride and Laven 1976).
The mature overstory was not readily damaged by
these fires, yet fuel accumulations are now large
enough to virtually assure destruction of the
mature stand. Prescribed fire can be used successfully to reduce these accumulations, but care
must be taken to minimize tree damage and control
the fire.
Enhancement and Management of Watershed Resources
The application of prescribed fire may provide
a variety of watershed and wildlife benefits.
Foremost among these is a reduction in the impacts
of severe wildfires. In recent years, wildfires
have frequently burned under the most extreme
conditions due to suppression of low and moderate
intensity wildfires, a high incidence of humanrelated ignitions during severe fire weather, and
a possible buildup of fuels because of active fire
suppression. Fire frequencies also may have
The intensity and effects of a prescribed fire
in chaparral may necessarily be greater than those
associated with prescribed burning in coniferous
forests or other woodlands. In conifer forests,
light ground fires with flame lengths less than
1/2 m could be used to achieve good fuel reduction. Flame lengths greater than 2 m could well
be excessive, causing undue damage to tree crowns
and boles, and the forest floor. In the chaparral
however, flame lengths greater than 2 to 3 m may
be necessary to propagate the fire and attain
desired fuel reduction. The amount of soil heating can be acceptable since the duration of heating is short and the alternative is burning under
wildfire conditions with possibly extreme fire
effects. Flame lengths in themselves are not here
a cause for concern, as they are in forest understory burning where canopy damage must be avoided.
PLANNING THE PRESCRIBED FIRE
Site Selection
The selection of sites for prescribed burning
on the National forests is an interdisciplinary
process involving professionals from fire, resource, wildlife, and planning disciplines.
Priorities are determined by the land and resource
management objectives specified in the National
forest management plan. A prescribed fire may
have one or more major resource objectives related
to fire hazard reduction, range improvement,
sediment and flood management, or wildlife habitat
improvement. These objectives are important in
determining the size, layout, season, intensity,
and frequency of burning in the prescribed fire
operation. They will also determine the proportion of the area to be burned within the planned
perimeter. For these reasons, a clear statement
of resource objectives is necessary for planning
and evaluating the prescribed fire.
503
For example, if fire hazard reduction is the
primary goal, the resource objectives might have
the following form:
Within a 5-km radius of residential communities
and for Santa Ana conditions with windspeeds of
60 km/h, (a) reduce long-range spotting to
distances less than 200 m and (b) maintain 50
percent of the chaparral with fuels that will
propagate fire at a rate of spread less than
0.4 m/sec.
The fire planner can use existing models (for
example, see Helfman and others 1975) to evaluate
the effects of different patterns of prescribed
burning on wildfire behavior in specific areas of
terrain and chaparral. In this way, different
burning options for the management area can be
compared so as to determine if the resource objectives are realistic. When the primary goals are
forest protection, flood and debris control, or
wildlife habitat improvement, similarly specific
resource objectives can be stated.
Environmental Analysis
An essential step in planning the prescribed
fire is the environmental analysis. This analysis
weighs the possible benefits and impacts of the
management action and outlines mitigating measures
that may be required. It serves as a compendium
of information on the vegetation, wildlife, sensitive or threatened and endangered species, soils,
and archaeological or cultural resources of the
project area.
Project Layout and Preparation
The size and extent of the prescribed fire are
determined jointly by the fire management officer
and the appropriate resource officers. The
planned fire perimeter is designed for ease of
containment within the framework of the burning
objectives and requirements of the environmental
analysis. Often, the burn can be easily enlarged
or reduced to improve the operation while still
achieving the planned objectives.
Whenever possible, existing barriers to fire
propagation should be used as control points. Not
only are existing roads and fuelbreaks useful, but
natural barriers such as ridge lines, riparian
areas, and age-class boundaries in the chaparral
can be used effectively for containment. Prescribed fires are often conducted under conditions
that are just severe enough to propagate the fire.
Changes in humidity or topography may have a
strong influence on the rate of spread and can be
used to contain the fire. The construction of
artificial control lines should be minimized due
to their high cost and possible soil disturbance.
Understory burning in riparian areas, such as
California live oak woodlands, can provide an
effective control line for broadcast burning
chaparral. If California black oak or mixed pine
504
forests are present in adjacent areas, they should
be understory burned under low intensity conditions before the planned chaparral burn. If high
accumulations of fuel are present around isolated
groups of trees within the planned chaparral fire
perimeter, hand or mechanical clearing in their
vicinity may be required to assure their survival.
The burning prescription should be designed to
meet the specific resource objectives for the
planned fire. Guidelines for developing a prescription are available (Green 1981); they require
a knowledge of the local fuels, terrain, and
weather behavior. Conditions required to propagate fire and achieve reasonable objectives in one
stand may be extreme in another. Fuels information, including total biomass and especially the
dead fuel loading and live fuel moistures, should
be gathered from a range of locations representing
the different aspects, vegetation types, and
terrain present within the fire area. Some interpretation of the available prescription guidelines
may be necessary since the important variables
influencing fire behavior will strongly interact.
For example, an area with relatively low dead fuel
volumes may require a prescription with relatively
low relative humidity and moderate windspeeds in
order to achieve burning objectives. It is important that the forest officer in charge of the
prescribed fire be familiar with fire behavior in
the local fuels and have the experience to determine realistic objectives and prescriptions.
A knowledge of regional and local weather
conditions is imperative for a successful prescribed fire. Foremost is a knowledge of the
probability of dangerous fire weather during or
after the burn. High pressure systems that create
strong Santa Ana winds may develop rapidly, so it
is important to have reliable weather forecasts
before, during, and after the fire. Local weather
conditions should also be monitored for a minimum
of 1 week before the burn, and the trends in
humidity and wind for the day should be estimated.
If you are "in prescription" at 1000 h, you must
have a reasonable idea whether or not you will
still be in prescription at 1400 h.
When local fuels and expected weather conditions are known, fire behavior may be partly
controlled by the nature of the planned ignition
pattern (Martin and Dell 1978). In heavy fuels
with a high proportion of dead material, backing
fires may be required to control the rate and
progress of burning and to contain the fire. In
lighter fuels, head fires or multiple ignitions
may be required to achieve an acceptable fuel
reduction or fire coverage. Areas of flashy fuels
or higher dead material accumulations may be used
to build heat and propagate fire into upslope
areas of less flammable vegetation.
The placement and requirements for fire suppression crews should be determined by a potential
escape analysis from which clear action plans can
be developed to control problem areas in the fire.
The burning operation for large fires can also be
broken into stages, each of which should be
brought to a degree of completion before crews
proceed to the next.
The burning objectives should provide an
assessment of the fire behavior required, including proportion of the area to be burned, fraction
of the litter layer to be consumed and allowable
flame height (in forest stands), rates of spread,
and amount of standing vegetation consumed. These
factors should be subjectively assessed as the
burning operation proceeds. A more complete
evaluation should be conducted following the
prescribed fire to determine (1) whether resource
objectives were fulfilled, (2) if any adverse fire
effects occurred and how they should be minimized
in future operations, and (3) if improvements are
needed in ignition patterns and holding operations.
CASE HISTORIES
Operational prescribed fires conducted recently
on the Descanso District of the Cleveland National
Forest have demonstrated that large prescribed
fires can be conducted safely in a variety of
chaparral and woodland communities. Four of
these, the Noble Canyon, Kitchen Creek, Troy
Canyon, and Mt. Laguna-Flathead Flats projects,
illustrate the use of prescribed fire under a
variety of conditions. Site characteristics and
burning conditions of these fires are shown in
tables 1 and 2.
Noble Canyon
The first large prescribed fire in southern
California was the 400-ha Noble Canyon Fire conducted June 13-14, 1978, at the beginning of the
summer drought. The primary objective of this
fire was the 100 percent reduction of the dead
fuels and fine live fuels in 50 to 70 percent of
the heavy chaparral on the site.
The Noble Canyon project presented a complex
situation (fig. 1). The site included a variety
of terrain and vegetation, including steep hill
slopes covered by 60-year-old chaparral, California live oak woodlands along the riparian
zones, and California black oak-Jeffrey pine
woodland along the upper project boundary.
Preburn treatments included hand and mechanical
line construction, understory burning in the oak
communities, and a few preparatory burns (fig. 1).
Existing or recleared roads were used as control
lines along 7 km of the project boundaries.
Handlines were also constructed through the chaparral over a distance of. 1.8 km. The mixed oakpine woodland was understory burned when the
annual grasses there were still green. Dead
leaves and needle litter carried this fire with
little reduction in live understory fuels.
Figure 1--Topography and layout of the 400-ha
Noble Canyon prescribed fire. The planned fire
perimeter is indicated by cross-hatching, and the
actual burn boundaries are shown by the dotted
line. Unburned islands occurred on the main hill
slope, and two out-of-bounds fire runs occurred at
the west perimeter. The fire perimeter could have
been easily extended to the paved road at the
lower right and to the riparian area at the upper
right.
Weather observations prior to the fire revealed
that the normal southwesterly airflow pattern,
humidity recovery, and the marine influence
occurred by 1800 h, and the desert influence and
low humidities (20 to 25 percent) returned at
approximately 0200 h.
The prescribed fire was ignited by two crews
using hand-held drip torches. They began by
burning the upper project perimeter with a backing
fire. Then they moved down the flanks and across
the lower boundary, burning the lower reaches and
most of the hill slopes with a head fire. Flame
lengths on the hill slopes averaged 3 to 4 m with
a maximum of 8 m.
Two small burns were ignited outside the
project perimeter by spotting across areas of
untreated riparian woodland. When these occurred,
burning crews were held in place on the main fire
while holding crews concentrated on control of the
out-of-bounds fires. These were contained at a
total size of 1.5 to 2 ha. No holding problems
were encountered where the woodland understory had
been previously prescribed burned.
With the onset of marine influence at about
1800 h, the relative humidity rose above 35 to 40
percent and fire could not be sustained in the
standing chaparral. Recovery of higher relative
humidity and lower air temperatures proved effective in suppressing fire activity.
505
Table 1--Site characteristics of four prescribed fire projects
Project
and date
Noble Canyon
6/13-14/78
Objectives
Fuelbreak
construction
and fuel
reduction
Vegetation
Size
ha
400
Mixed oak-pine
woodland upper
elevation
Slope
Percent
35 to 75 on
hill slopes
Elevation
m
1130 to 1600
60+
1340 to 1580
Chaparral
stand age
(approx.)
Aspect
All, slopes
predominantly
SW
60
East
35
Mixed chaparral
on hill slopes-Af., Cg, Qd
Qag woodland in
major drainages
2
Kitchen Creek
11/14-15/79
Fire effects
research
Qd-dominated
mixed chaparral-Qd, Cg, Af,
Ag, Cl
Troy Canyon
4/9, 14/80
Wildlife
habitat
and fuel
reduction
Qag woodland
with mixed
chaparral on
hill slopes-Cb, Af, Qd
120
40 to 50 on
hill slopes
1280 to 1520
Laguna Mountain
2/12
through
5/29/80
Reduce
activity
fuels,
fuelbreak
construction
P. jeffreyi-Q. kelloggii
woodland, P.
coulteri with
Ag understory
140
0 to 35
1720 to 1800
35
N-S
trending
canyon
Predominantly
W-SW
70
1
'
Af--Adenostoma fasciculatum, Ag—Arctostaphylos glandulosa, Cb—Cercocarpus betuloides, Cg—Ceanothus
greggii, Cl--Ceanothus leucodermis, Qag--Quercus agrifolia, Qd--Quercus dumosa.
Table 2--Burning conditions for four prescribed fires
Project
Air
temperature
°C
Noble Canyon
12 to
Test fires:
5/21/79
7/25/79
8/15/79
27
30
24
Troy Canyon
Laguna Mountain
1
506
Percent
15 to 26
Kitchen Creek
Relative
humidity
15
13 to 22
9 to 19
Windspeed and
direction
Fuel
stick
km/h
Live fuel
moisture
Fraction of
chaparral dead
------------Percent---------
5 to 21
NW, morning;
SW, afternoon
4.5
75 (Af)
30
21 to 27
Wind run-4.8 gusts
to 24; NE
4.5
78 (Qd)
<20
25
25 to 30
38 to 42
<8; NE-SE
<13; NE-SE
<6; NE-SE
21 to 33
10 to 16
NW
28 to 50
50 to 72
in P. coulteriA. glandulosa
stands
0 to 19
SE-SW
See footnote 1, table 1, for key to abbreviations.
5.25
9
10 to 15+
130 (Qd)
100 (Qd)
88 (Qd)
80 (Af)
80 to 110 (Ag)
<25
60 to 70 in P.
coulteri-A.
glandulosa
stands
From the experience gained in this project, it
was apparent that the operation could have been
improved in two areas. First, the construction of
handlines could have been avoided on both the
south and northeast perimeters. The fire could
have been easily extended on the south to the
existing county highway and an abandoned road
(fig. 1) without creating traffic control problems. On the northeast, the perimeter could have
been extended by firing along the canyon bottom
north to the Noble Canyon Road. The existing
handline on the northeast proved to be a poor
location for firing since the backing fires
ignited there progressed only poorly down or along
the hill slope and the prevailing wind tended to
carry firebrands across the line. Firing from an
extended line in the canyon bottom would have been
upslope and in the lee side of the hill. Second,
the understory of the live oak woodlands could
have been burned without the construction of
handlines. Burning under relative humidities
greater than 35 percent and with higher chaparral
live fuel moistures during the early spring would
have effectively contained the fire at the woodland perimeter.
The Noble Canyon project successfully demonstrated prescribed burning in old chaparral and
rugged terrain. Fire intensities were moderate
and there were no serious adverse effects. It
provided valuable experience in the planning and
execution of a large prescribed fire, and demonstrated the need for complete pretreatment operations, and the effectiveness of late afternoon
humidity recovery in controlling fire spread.
Kitchen Creek Research Prescribed Fires
A series of prescribed fires conducted jointly
by the Chaparral Research and Development Program
of the Pacific Southwest Forest and Range Experiment Station and the Descanso District, Cleveland
National Forest, was begun in the summer of 1979.
This project was designed to provide replicated
fires in mixed chaparral in which fire effects and
biological recovery processes could be studied.
It was located on east-facing hill slopes above
Kitchen Creek on southern Laguna Mountain. The
chaparral, last burned in a wildfire in 1944,
consisted primarily of scrub oak, chamise, and two
species of Ceanothus--C. greggii and C. leucodermis Greene. Standing biomass in stands of scrub
oak was 18.5 MT/ha.
Our research needs required strip fires on a
uniform slope and aspect, with the strips running
perpendicular to the contours so that any sediment
movement would be restricted to the strip. Handlines were cut on an intermediate ridge at the top
of the slope, and some preparation burning was
conducted on the flank of a hanging valley beyond
this ridge. In the event of a major escape,
containment could be made at the top of the main
ridge where there is an age-class boundary with
chaparral burned during 1970. Areas 30 m wide
were hand cleared on the north and south project
boundaries to provide both lateral fire containment and harvested areas for research purposes.
Control lines 2 m wide were also cleared on the
strip boundaries, and the dried brush was burned
under high humidity conditions.
Burning trials conducted throughout the late
spring and summer provided an opportunity to
observe fire behavior as live fuel moisture in new
growth was reduced from 130 to 78 percent under
continuously dry weather conditions. These fires
showed generally low flame heights and poor rates
of spread despite relatively hot and dry weather
(table 2), and indicated that relatively hot
prescription conditions and mass ignition would be
required to achieve the desired fire coverage and
fuel reduction.
Three successful prescribed fires were conducted November 14-15, 1979 under relatively
severe weather using a helitorch for ignition
(table 2) (fig. 2). Strips measuring approximately 30 by 200 m were burned at the north end
and center of the project on the first day. These
fires were well behaved, showed slow runs with
little lateral spread, and partially (60 to 70
percent) burned each strip after several passes of
the helitorch.
Wind direction was from the northeast so the
southern or leeward edge of each strip was ignited
first, with successive passes of the helitorch
moving further toward the windward edge. This
ignition pattern gave the best possible visibility
and minimized the chance of burning areas outside
of the intended strip. Several passes of the
helitorch were required to build heat and obtain
good fire coverage.
Weather conditions during the second day remained similar to those of the first. However,
Figure 2--Strip burning with a helitorch in mixed
chaparral at Kitchen Creek.
507
several of the brush piles from the adjacent
hand-cleared area were inadvertently ignited by
firebrands. Windspeed also increased to 7.5 km/h
(gusts to 32 km/h), and fire spread into standing
brush outside of the project boundary. During the
burning operation, the Laguna Hot Shot crew was
strategically located for fire control at the
upper end of the project, and the helicopter used
for ignition had a water bucket available at the
helibase used for the operation. When fire spread
beyond the project boundary, burning was suspended
and these crews suppressed the out-of-bounds fire.
Fire runs outside the project boundary moved
slowly upslope and posed no control problems.
Our experiences at Kitchen Creek have demonstrated the importance of site fuel properties.
Even though it is fully mature, the mixed chaparral at this site has species with characteristically low dead fuel accumulations and flammability. Windspeeds, humidity, and fuel moisture that
might produce severe burning conditions in other
chaparral community types are required to propagate fire in these stands. This prescribed fire
was successful because we were able to conduct a
series of burning trials under successively more
severe conditions and refine our prescription.
Fire runs did leave the intended project boundary
due to spotting and increased windspeed, but we
were fully prepared to deal with these. We also
knew from past experience in this fuel type that
such problems would not produce a large escaped
fire. This project also demonstrated that a fire
can often propagate in a stand only if a sufficient amount of heat is initially generated by use
of natural fine fuels or special ignition techniques such as the helitorch.
Troy Canyon
A prescribed fire was conducted along Troy
Canyon on April 9 and 14, 1980 in order to reduce
the fine fuels in the understory and forest floor
of a California live oak woodland, and to produce
a mosaic of different age classes in the adjacent
mixed chaparral community. The chaparral in this
area was last burned during a wildfire in 1944,
and was dominated by chamise, Ceanothus greggii,
and scrub oak.
mately 6 km of understory burning was conducted
over 2 days using a crew of six persons for ignition and needed suppression activities. Burning
was conducted with a relative humidity ranging
from 20 to 33 percent and 12 to 20 km/h winds out
of the northwest. Live fuel moistures were generally at the lowest point of the year. Flower buds
in the Ceanothus greggii were beginning to burst;
otherwise, there was little new growth or rise in
the dormant season fuel moistures apparent.
Good fire behavior and results were achieved.
Fire did carry into some oak trees, but it burned
in the canopy for less than 10 seconds and little
damage was produced. A general pruning of the
lower canopies was achieved. A partial reduction
of the oak forest floor occurred (fig. 3), but a
large input of fresh oak litter from scorched
leaves was later observed. A second burn in 1 to
3 years may be desirable to further reduce litter
accumulations in the oak woodland.
The understory fires were carried by the wind
up the west-facing hill slopes and stopped at the
ridge line with little carryover onto the adjacent
east-facing slope. The latter slopes were shaded
and apparently had higher live fuel moistures.
Burning conditions would propagate fire uphill
with the wind, but would not allow it to carry
down the opposite slope. These chaparral fires
achieved good fuels reduction and produced the
desired mosaic pattern. Overall, about 30 to 50
percent of the chaparral along the canyon reach
was burned. Burning was suspended when weather
forecasts indicated developing Santa Ana wind
conditions, and patrols were assigned to monitor
the burned area for possible outbreaks.
This project successfully used vegetation and
fuel differences on different aspects and late
afternoon humidity recovery to effectively contain
the prescribed fire. A substantial area of oak
woodland and adjacent chaparral was burned in
From past experience at Noble Canyon, Kitchen
Creek, and elsewhere in this area, it was expected
that prescription conditions with low humidity and
moderate (12 to 20 km/h) winds would produce
well-behaved fire runs. Humidity recovery late in
the day was also expected to drastically reduce
fire activity, especially on north- and eastfacing slopes. This area was bounded on the east
by areas of low-flammability chaparral and a
moist, grass fuelbreak system, and on the west by
a highway. These control areas would effectively
contain any fire leaving the project area. For
these reasons, no control lines were constructed.
The light fuels and forest floor under the oaks
were ignited by hand-held drip torches. Approxi-
508
Figure 3--Understory burning and fuels in a California live oak woodland at Troy Canyon.
rough terrain with only a small fire crew and no
established control lines.
Laguna Mountain Understory Burns
The conifer—oak woodland found on Laguna Mountain is one of the most important areas for recreation and wildlife habitat in San Diego County.
Large areas have no known fire history and support
heavy accumulations of forest floor litter and
downed woody fuels. The Laguna Mountain area is
subject to less than one ignition from lightning
6
each year, but illegal campfires are a problem.
Wildfires in this area would be expected to destroy the pine—oak overstory, and result in dense
manzanita thickets on some aspects. A second
wildfire burning in the regenerated manzanita and
young pine could eliminate the pine from the site.
A series of prescribed fires was initiated in
the area north of the Mount Laguna Air Force
Station in February 1980 in order to reduce the
accumulations of forest floor and manzanita fuels
in the woodland and encourage regeneration of the
forest species. Stand composition varies from an
association of. Jeffrey pine and California black
oak with some Ceanothus palmeri Trel. in the
understory on more mesic slopes to open stands of
Coulter pine (Pinus coulteri D. Don) with an
Arctostaphylos glandulosa Eastw. understory on the
drier west—facing aspects (fig. 4). The manzanita
stand is about 2 m high with a biomass of 19
MT/ha. The underlying forest floor averages 8 to
10 cm in depth, and pine needle accumulations in
the manzanita contribute to the stand's flammability.
The 185—ha project was subdivided into nine
units ranging from 5 to 40 ha in size. Existing
roads and trails were used to delineate units
where possible, and hand clearing was used to
complete the control lines. The most difficult
prescribed burning problem in this project was in
the areas of. Coulter pine and manzanita; caution
was needed to avoid damaging the canopies of the
overstory trees.
Firing with hand—held drip torches began with a
backing fire ignited along the top of the ridge on
the leeward side of a block. Good fire propagation and minimal tree damage in Coulter pine
stands were obtained when the relative humidity
was above 70 percent. Below this value the fire
became too intense, and hose lays and handtool
work were necessary to control flame lengths and
prevent damage to the tree crowns. Some crown
scorch did occur, but less than 5 percent of the
trees were badly damaged or killed. Good reduction of fine fuels was achieved in the manzanita
and forest floor, but heavy accumulations of the
larger size class dead material remain. A second
6
Personal communication from D. Studebaker,
Cleveland National Forest, Alpine, Calif.
Figure 4--Coulter pine with manzanita understory
fuels on Laguna Mountain.
or third fire is needed to further reduce forest
floor and standing dead material accumulations,
especially after scorched needles fall and provide
new ground fuel to carry the fire. The manzanita
is also rapidly resprouting, and subsequent fires
could reduce its density and growth rates.
High humidity and low windspeeds are required
to successfully burn mixed conifer—chaparral
stands with heavy fuel loadings, vet good fuel
reduction can be obtained in these areas with
minimal overstory tree damage. Repeated burns may
be necessary to achieve desired fuel reductions
and wildfire protection for these valuable areas.
CONCLUSIONS
Prescribed fire is an important chaparral
management technique that may be used to meet
resource objectives including fire hazard reduction, wildlife habitat improvement, sediment
management, and the reduction of adverse wildfire
effects. It may be used successfully in a variety
of chaparral fuel types and weather conditions.
Successful prescribed fires require:
° Management by an experienced fire management
officer
° Knowledge of stand fuel characteristics, particularly the proportion of fine dead fuels, total
fuel loading, live fuel moisture, and the changes
509
in fuel properties in different chaparral community types
° Knowledge of expected weather behavior,
including diurnal patterns of relative humidity,
onset of desert influence conditions, daily
changes in wind direction, and especially the
likelihood of severe burning conditions
° Knowledge of differences in fuels and microclimate with terrain, including north- and southfacing slopes or trends with elevation
° Consideration of transient (nonsteady state)
fire behavior, including the use of special ignition techniques and light fuels to control fire
spread and activity
° Careful planning of fire control lines along
natural features such as ridge lines, fuel-type
boundaries (for example, conifer-oak woodland or
riparian woodland with chaparral), and chaparral
age-class boundaries; or the use of weather and
fuel conditions to contain the fire
The Laguna-Morena Demonstration has been a
focal point for development and refinement of
prescribed burning techniques in the chaparral.
Careful application of prescribed fire and the
knowledge acquired here has the potential for
substantial resource benefits in chaparral
throughout California.
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